1. Field of the Invention
The present invention relates to a zoom lens system that constitutes a miniaturized zoom optical system for a video camera or a electronic still camera that use an image sensor such as a CCD or a CMOS, etc., especially for use in a surveillance camera.
2. Description of Related Art
In recent years, there has been an increasing demand for small surveillance cameras in offices and in train stations, etc. Conventionally, a surveillance camera is provided with a fixed focal-length lens selected from a plurality of fixed focal-length lenses in accordance with usage. However, in order to handle various requirements in regard to installation of such a surveillance camera, a zoom lens has been in demand. Recently, mainly retrofocus zoom lens systems that are low-pixelization compatible, i.e., compatible with a VGA (Video Graphics Array: 640×480 pixel image resolution), etc., have become predominant.
An example of a conventional zoom lens system is disclosed in Japanese Unexamined Patent Publication No. 2006-39094.